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Hourly Averaged WKT O 3 and CO observations. Ozone and CO are highly correlated throughout the summer. Implies that sources are largely co-located.
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Statistics for WRF-STILT PBL height verification against TexAQS-2006 profiler observations. Relative bias and standard deviation (rel.bias and rel.sd) are defined as the bias and error standard deviation, normalized by the mean observed value.
457m, September 2006
Relative Regional Contributions to
Modeled CO Mid-Day (19 GMT/14 CDT)
Observed and Simulated CO
Cumulative Sensitivity Footprint for WKT for Sept 2006 Mid-Day (14:00 CDT).
If footprint were rearranged in the shape of a circle:
50% within 838km
Simulated Fossil Fuel CO
Locations of TEXAQS boundary layer profilers (lower case identifiers). Those outside of innermost domain are plotted in green. The closest radiosonde location (FWD) is shown in blue.
NEI99 x (1/ 2.1)
*The CO background was calculated in the manner of Gerbig et al. (2003) using a climatological CO distribution from 1999-2000. An offset of 15 ppb was applied to match the lower envelope of the observations. Longitudinal variations were neglected.
*Fire simulations were not available for STILT, so fire CO from the FLEXPART-ECMWF run was applied for comparison with observations.
Tall-tower observations of pollution from near-field sources in central Texas
during the Texas Air Quality Study 2006
A.E. Andrews1, E. Kort2, A. Hirsch3, J. Eluszkiewicz4, T. Nehrkorn4, A.M. Michalak5, A. Stohl6, G. Petron3, G. Frost3,
K. Gurney7, S.C.Wofsy2, W.M.Angevine3, A.B. White1, S.J. Oltmans1, S.A. Montzka1, P.P. Tans1
1NOAA Earth System Research Laboratory, Boulder, CO; 2Harvard University, Cambridge, MA; 3Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO;
4Atmospheric and Environmental Research, Inc., Lexington, MA; 5University of Michigan, Ann Arbor, MI; 6Norwegian Institute for Air Research (NILU), Kjeller, Norway; 7Purdue, University, West Lafayette, IN
ABSTRACT:The NOAA Earth System Research Laboratory has been measuring CO2, CO and basic meteorology from a television transmitter tower outside of Waco, TX since 2001. This site is identified in the NOAA network as WKT. Sample intakes are located at 30, 122 and 457 meters above ground level (magl). From July through November 2006, O3 measurements were added at 9 and 457 magl to support the Texas Air Quality Study (TexAQS 2006). There are several large point sources and metropolitan areas in the vicinity of the tower with distinct chemical signatures. Here, we evaluate the extent to which the Stochastic Time Inverted Lagrangian Transport (STILT) model reproduces pollution events that were observed at the tower during summer and fall 2006. For this study, STILT is driven by customized output from the WRF model v 2.2, which was run with a 2 km grid surrounding the tower embedded in a 10 km nest that covers most of the southern and eastern US and a 40 km nest that includes all of North America. Inaccurate representation of atmospheric transport is a major source of error in inverse estimates of fluxes of CO2 and other gases, and we selected this period for in depth analysis in part because a dense network of radar profilers was deployed for TexAQS 2006. The radar profilers report wind and boundary layer height, which can be used to evaluate the fidelity of the simulated transport. We have quantitatively compared the STILT-WRF results with similar output from the FLEXPART particle dispersion model driven by high-resolution ECMWF meteorology fields. We have used several different emissions inventories to evaluate model-to-model differences and differences between modeled and observed pollution influences.
Sampling Footprints and Evaluation of STILT-WRF Transport
Left: Radiosonde sites used in the WRF wind field verification. Locations plotted in red are only in the outermost domain (d01, 40km); green or blue locations are contained within domains (d02, 10km), those in blue are located within the 2km domains (d03, d04, and d05, 2km).
Right: RMS error statistics for the 10km domain for Fall 2006
Measured and Modeled Time Series from STILT and FLEXPART
and possible implications for air quality in central TX
Point Source Plumes
Bakwin, P. S., P. P. Tans, D. Hurst and C. Zhao, (1998), Measurements of carbon dioxide on very tall towers: Results of the NOAA/CMDL program. Tellus, 50B, 401-415.
Gerbig, C., J. C. Lin, et al. (2003). "Toward constraining regional-scale fluxes of CO2 with atmospheric observations over a continent: 1. Observed spatial variability from airborne platforms." Journal of Geophysical Research-Atmospheres108(D24).
Gerbig, C., J. C. Lin, et al. (2003). "Toward constraining regional-scale fluxes of CO2 with atmospheric observations over a continent: 2. Analysis of COBRA data using a receptor-oriented framework." Journal of Geophysical Research-Atmospheres108(D24).
Lin, J. C., C. Gerbig, et al. (2003). "A near-field tool for simulating the upstream influence of atmospheric observations: The Stochastic Time-Inverted Lagrangian Transport (STILT) model." Journal of Geophysical Research-Atmospheres108(D16).
Peters, W., A. R. Jacobson, et al. (2007). "An atmospheric perspective on North American carbon dioxide exchange: CarbonTracker." Proceedings of the National Academy of Sciences of the United States of America104(48): 18925-18930.
Turnbull, J. C., J.B. Miller, S. J. Lehman, P.P. Tans, R.J. Sparks, and J. Southton, (2006). Comparison of 14CO2, CO, and SF6 as tracers for recently added fossil fuel CO2 in the atmosphere and implications for biological CO2 Exchange, GRL, 33, L01817, doi:10.1029/2005GL024213.
Trajectories for observed plumes from the TexAQS 2006 wind profiler network
CO2 point sources
CO/CO2 emissions ratios for observed plumes.
For more information contact:
NOAA Earth System Research Laboratory
Global Monitoring Division
Fall Meeting of the American Geophysical Union
San Francisco, CA, 15-19 December 2008